According to FIG. 6 a conventional bicycle shock absorbing device generally includes a cylinder 71 that is fixedly connected to a bicycle frame such as the seat tube and a plug 72 having a first end thereof movably received in the cylinder 71. An end member 70 is connected to a second end of the plug 72 and is fixedly connected to another part of the bicycle frame such as a down tube. A first collar 73 is mounted to the cylinder 71 and a second collar 74 is connected to the end member 70. A spring 75 is mounted to the plug 72 and the cylinder 71, and is biased between the first collar 73 and the second collar 74. A container 77 is connected to the cylinder 71 so as to store hydraulic oil therein which results in damping force when the plug 72 moves relative to the cylinder 71. Two adjusting buttons 76 and 78 are located at the cylinder 76 and the end member 70 so as to adjust the "stiffness" of the shock absorbing device according to practical needs when the bicycle is ridden on rugged roads. It is inconvenient for the rider to adjust the shock absorbing device on the two adjusting buttons 76 and 78.
The present invention intends to provide a shock absorbing adjusting structure that allows the rider to adjust the shock absorbing device by operating the only one adjusting lever.